Methods and Systems for Dithering Active Sensor Pulse Emissions

ABSTRACT

One example device comprises a plurality of emitters including at least a first emitter and a second emitter. The first emitter emits light that illuminates a first portion of a field-of-view (FOV) of the device. The second emitter emits light that illuminates a second portion of the FOV. The device also comprises a controller that obtains a scan of the FOV. The controller causes each emitter of the plurality of emitters to emit a respective light pulse during an emission time period associated with the scan. The controller causes the first emitter to emit a first-emitter light pulse at a first-emitter time offset from a start time of the emission time period. The controller causes the second emitter to emit a second-emitter light pulse at a second-emitter time offset from the start time of the emission time period.

BACKGROUND

Active sensors, such as light detection and ranging (LIDAR) sensors,radio detection and ranging (RADAR) sensors, sound navigation andranging (SONAR) sensors, among others, are sensors that can scan asurrounding environment by emitting signals toward the surroundingenvironment and detecting reflections of the emitted signals.

For example, a LIDAR sensor can determine distances to environmentalfeatures while scanning through a scene to assemble a “point cloud”indicative of reflective surfaces in the environment. Individual pointsin the point cloud can be determined, for example, by transmitting alaser pulse and detecting a returning pulse, if any, reflected from anobject in the environment, and then determining a distance to the objectaccording to a time delay between the transmission of the pulse and thereception of the reflected pulse. As a result, for example, athree-dimensional map of points indicative of locations of reflectivefeatures in the environment can be generated.

SUMMARY

In one example, a device comprises a plurality of emitters including atleast a first emitter and a second emitter. The first emitter emitslight that illuminates a first portion of a field-of-view (FOV) of thedevice. The second emitter emits light that illuminates a second portionof the FOV. The device also comprises a controller that obtains a scanof the FOV. Obtaining the scan involves the controller causing eachemitter of the plurality of emitters to emit a respective light pulseduring an emission time period associated with the scan. Causing eachemitter to emit the respective light pulse involves the controllercausing the first emitter to emit a first-emitter light pulse at afirst-emitter time offset from a start time of the emission time period,and causing the second emitter to emit a second-emitter light pulse at asecond-emitter time offset from the start time of the emission timeperiod.

In another example, a method involves causing a plurality of emitters toemit a plurality of light pulses during a first emission time periodassociated with a first scan of a field-of-view (FOV). A first emitterof the plurality of emitters may be configured to illuminate a firstportion of the FOV. A second emitter of the plurality of emitters may beconfigured to illuminate a second portion of the FOV. Causing theplurality of emitters to emit the plurality of light pulses may involvecausing the first emitter to emit a first-emitter light pulse at afirst-emitter time offset from an end time of the first emission timeperiod, and causing the second emitter to emit a second-emitter lightpulse at a second-emitter time offset from the end time of the firstemission time period. The method also involves obtaining the first scanbased on measurements of light from the FOV received by a plurality ofdetectors during a first detection time period that begins after the endtime of the first emission time period.

In yet another example, a device includes a transmitter that emits aplurality of light beams during a first emission time period associatedwith a first scan of a field-of-view (FOV) of the device. The pluralityof light beams is spatially arranged to illuminate respective portionsof the FOV. The first emission time period has a start time and an endtime. The transmitter emits a first light beam of the first plurality oflight beams toward a first portion of the FOV at a first-portion timeoffset from the start time of the first emission time period. Thetransmitter emits a second light beam of the first plurality of lightbeams toward a second portion of the FOV at a second-portion time offsetfrom the start time of the first emission time period. The device alsoincludes a receiver that intercepts light from the FOV illuminated bythe transmitter.

In still another example, a device comprises a controller that obtains asequence of scans of a field-of-view (FOV) of the device. The devicealso comprises a transmitter that emits, for a first scan of thesequence of scans, a first plurality of light pulses in a particularspatial arrangement and according to a first plurality of time offsetsbetween emission times of the plurality of light pulses. The device alsocomprises a receiver that includes a plurality of detectors. Eachdetector of the plurality of detectors may be aligned with a respectiveportion of the FOV illuminated by a respective light pulse of the firstplurality of light pulses.

In still another example, a system comprises means for causing aplurality of emitters to emit a plurality of light pulses during a firstemission time period associated with a first scan of a field-of-view(FOV). A first emitter of the plurality of emitters may be configured toilluminate a first portion of the FOV. A second emitter of the pluralityof emitters may be configured to illuminate a second portion of the FOV.Causing the plurality of emitters to emit the plurality of light pulsesmay involve causing the first emitter to emit a first-emitter lightpulse at a first-emitter time offset from an end time of the firstemission time period, and causing the second emitter to emit asecond-emitter light pulse at a second-emitter time offset from the endtime of the first emission time period. The system also comprises meansfor obtaining the first scan based on measurements of light from the FOVreceived by a plurality of detectors during a first detection timeperiod that begins after the end time of the first emission time period.

These as well as other aspects, advantages, and alternatives will becomeapparent to those of ordinary skill in the art by reading the followingdetailed description with reference where appropriate to theaccompanying drawings. Further, it should be understood that thedescription provided in this summary section and elsewhere in thisdocument is intended to illustrate the claimed subject matter by way ofexample and not by way of limitation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified block diagram of a device, according to exampleembodiments.

FIG. 2 illustrates a LIDAR device, according to example embodiments.

FIG. 3 illustrates a cross-section view of a plurality of emitted beamsspatially arranged to scan respective portions of a FOV, according toexample embodiments.

FIG. 4 is a flowchart of a method, according to example embodiments.

FIG. 5 is a flowchart of another method, according to exampleembodiments.

FIG. 6A illustrates conceptual timing diagrams for a first scan of aFOV, according to example embodiments.

FIG. 6B illustrates conceptual timing diagrams for a second scan of theFOV, according to example embodiments.

DETAILED DESCRIPTION

Exemplary implementations are described herein. It should be understoodthat the word “exemplary” is used herein to mean “serving as an example,instance, or illustration.” Any implementation or feature describedherein as “exemplary” or “illustrative” is not necessarily to beconstrued as preferred or advantageous over other implementations orfeatures. In the figures, similar symbols typically identify similarcomponents, unless context dictates otherwise. The exampleimplementations described herein are not meant to be limiting. It willbe readily understood that the aspects of the present disclosure, asgenerally described herein and illustrated in the figures, can bearranged, substituted, combined, separated, and designed in a widevariety of different configurations.

I. Overview

Within examples, an active sensing system (e.g., LIDAR, RADAR, SONAR,etc.) may include a transmitter that transmits a plurality of signals(e.g., beams, pulses, etc.) spatially arranged (e.g., in a gridarrangement or other arrangement of adjacent signals) to scan respectiveportions of a field-of-view (FOV).

In one example, a LIDAR device may include multiple transmit/receivechannels arranged to scan respective portions of a FOV. For instance,the LIDAR device may include a transmitter that transmits a plurality oflight beams toward the FOV. Each light beam may illuminate a respectiveportion of the FOV. The LIDAR device may also include a plurality ofdetectors and a lens that focuses light from the FOV for receipt by theplurality of detectors. A first detector of the plurality may bearranged to intercept a first portion of the focused light from a firstportion of the FOV that was illuminated by a first light beam of theplurality of light beams. Similarly, a second detector may be arrangedto intercept a second portion of the focused light from a second portionof the FOV that was illuminated by a second light beam, and so on. Thus,each detector may be aligned with a corresponding transmitted light beamto define a respective transmit/receive channel of the LIDAR device.

With this arrangement, the multiple transmit/receive channels caninterrogate different portions of the FOV. For instance, each channelcan emit a pulse of light during an emission time period, and then“listen” for a reflected pulse during a detection time period followingthe emission time period. In some implementations, the LIDAR device maythen perform a subsequent scan of the FOV, which similarly includesanother emission time period followed by another detection time period,and so on. With this arrangement for instance, the LIDAR device canobtain a sequence of scans (e.g., periodically) of the FOV.

In some scenarios, a reflected portion of light that was originallytransmitted by a particular channel may be detected in one or more otherchannels (e.g., neighboring channels that scan portions of the FOVadjacent to the portion scanned by the particular channel), therebyresulting in spurious signal detection (e.g., “cross-talk”) by the otherchannel(s). Various factors may cause such cross-talk, such as opticaldistortions in the lens, distortions caused by dust particles on thelens, and/or reflectivity characteristics of objects in the scannedenvironment, among other factors.

In one scenario, transmitted light in a particular channel may bereflected by a retroreflector in a portion of the FOV scanned by theparticular channel. A retroreflector may include a device or surfacethat reflects a relatively higher fraction of incident light back (e.g.,into a relatively narrower cone, etc.) toward its source as compared toother types of reflectors. For instance, a road traffic sign may becoated with a retroreflector to improve visibility of the sign tovehicle drivers on the road. In this scenario, some portions of the(strong) reflected signal from the retroreflector may have sufficientamounts of energy to be detected by other (e.g., neighboring) channels(spuriously) as well as the particular channel that illuminated theretroreflector.

By way of example, a retroreflector may be located within a portion ofthe FOV scanned by a first channel. In this example, a light pulseemitted by the first channel may be reflected by the retroreflector, andthe reflected light pulse may then be detected at the first channel as arelatively strong signal. In this example, a time difference between theemission time of the emitted light pulse and the detection time of thereflected light pulse can be used to determine that the retroreflectoris at a distance of 50 meters from the LIDAR device. However, as notedabove, N additional channels may also receive portions of the reflectedlight pulse from the retroreflector as spurious signals. If the Nadditional channels had also emitted N respective light pulses at thesame emission time as the light pulse of the first channel, then thespurious signals detected by the N channels may be interpreted asreflections of the N light pulses from objects (at a distance of 50meters) within respective portions of the FOV scanned by the N channels.As a result, the spurious signals may prevent or interfere withdetection of actual objects present at the same distance of 50 meterswithin the respective portions of the FOV scanned by the N additionalchannels. For instance, a computing system that processes data from theLIDAR to generate a 3D map of the environment may render a map thatshows “ghost” retroreflectors at the 50 meter distance (e.g., instead ofshowing objects actually present at this distance).

Reducing this type of cross-talk error may be desirable in someapplications. For example, a LIDAR-equipped vehicle may be configured touse the LIDAR to detect objects (e.g., other vehicles, pedestrians,etc.) in the environment of the vehicle. In this example, if the LIDARis unable to scan significant portions of the environment near everyretroreflector (e.g., objects adjacent to a stop sign, etc.), then theLIDAR may be less reliable for object detection and/or operation of thevehicle.

To mitigate the effects of such cross-talk, in some examples, the LIDARdevice may include one or more light filters interposed between the lensand the plurality of detectors. The light filter(s) may reduce (orprevent) relatively weak spurious signals propagating toward anunintended transmit/receive channel. However, an extent of filtration bythe light filter(s) may be limited to allow propagation of non-spurioussignals through the light filter(s). Thus, the light filter(s) may stillallow propagation of some (relatively stronger) spurious signals (e.g.,having a similar amount of energy as that of non-spurious signals), suchas spurious signals associated with retroreflectors for instance.

Accordingly, some implementations herein may involve operating amulti-channel active sensor (e.g., LIDAR, SONAR, etc.) to mitigate theeffects of channel cross-talk associated with retroreflectors or othersources of spurious signals.

In a first example, one or more of the multiple transmit/receivechannels of the LIDAR device described above can be configured to emitrespective light pulses at different respective time offsets during afirst emission time period of a first scan of the FOV of the LIDAR. Forinstance, a first channel may emit a light pulse near the beginning ofthe first emission time period, a second channel may emit a light pulsenear the end of the first emission time period, and so on. After thefirst emission time period ends, the multiple channels of the LIDAR maythen begin “listening” for reflections of their respective emitted lightpulses during a first detection time period of the first scan. With thisarrangement for instance, if a retroreflector present at a distance of50 meters in a first portion of the FOV scanned by the first channelcauses spurious signal detections at N other channels that scan otherportions of the FOV, then the spurious signal detections may be mappedto a variety distances (e.g., 40-60 meters) due to the differencesbetween the emission times of the first channel and the N channels.Thus, in this example, the LIDAR can improve the quality of objectdetection at the range of 50 meters by spreading the spurious signaldetections associated with the retroreflector over a range of distances.

In a second example, where the LIDAR device obtain a sequence of scansof the FOV (e.g., periodically), the LIDAR device may be configured toadjust the respective emission time offsets assigned to a particularchannel for each scan in the sequence. For instance, in a first scan ofthe sequence, the first channel may emit a light pulse near thebeginning of the first emission time period and the second channel mayemit a light pulse near the end of the first emission time period. Next,in a second scan subsequent to the first scan, the first channel mayinstead emit a light pulse near the end of a second emission time periodof the second scan, and the second channel may instead emit a lightpulse near the beginning of the second emission time period, and so on.

Thus, with this arrangement, the emission times used by a particularchannel over the sequence of scans may be effectively dithered (e.g.,relative to a start or end of the respective emission time periods ofthe sequence of scans). As a result, for instance, if the particularchannel is “blinded” from detecting an object at a particular distance(e.g., 50 meters) during a first scan (due to a spurious signal fromanother channel), then the particular channel may be able to detect theobject during a subsequent second scan (because the spurious signal willbe instead mapped to a different distance in the second scan). Forinstance, actual signals reflected by an object illuminated by theparticular channel may be detected repeatedly as being at the sameparticular distance during successive scans by the particular channel(e.g., “coherent” detections). Whereas, spurious signals caused by aretroreflector illuminated by another channel may be detected repeatedlyas being at different distances (e.g., “incoherent” detections) duringthe successive scans.

In some implementations, the time offsets assigned to a particularchannel in each respective emission time period of the sequence of scanscan be based on a pseudo-random time offset sequence. For example, acomputing system can determine the pseudo-random time offset sequencethat is applied to one or more particular channels prior to the LIDARperforming the sequence of scans. However, in other implementations,varying the time offsets from one scan to another can be performed in avariety of different ways.

II. Example Sensor Systems and Devices

A non-exhaustive list of example sensors that can be employed hereinincludes LIDAR sensors, RADAR sensors, SONAR sensors, active IR cameras,and microwave cameras, among others. To that end, some example sensorsherein may include active sensors that emit a signal (e.g., visiblelight signal, invisible light signal, radio-frequency signal, microwavesignal, sound signal, etc.), and then detect reflections of the emittedsignal from the surrounding environment.

FIG. 1 is a simplified block diagram of a device 100, according toexample embodiments. As shown, device 100 includes a power supplyarrangement 102, a controller 104, a transmitter 106, one or moreoptical elements 108, a receiver 114, a rotating platform 116, one ormore actuators 118, a stationary platform 120, a rotary link 122, and ahousing 124. In some embodiments, device 100 may include more, fewer, ordifferent components. Additionally, the components shown may be combinedor divided in any number of ways.

Power supply arrangement 102 may be configured to supply, receive,and/or distribute power to various components of device 100. To thatend, power supply arrangement 102 may include or otherwise take the formof a power source (e.g., battery cells, etc.) disposed within device 100and connected to various components of the device 100 in any feasiblemanner, so as to supply power to those components. Additionally oralternatively, power supply arrangement 102 may include or otherwisetake the form of a power adapter configured to receive power from one ormore external power sources (e.g., from a power source arranged in avehicle to which device 100 is mounted) and to transmit the receivedpower to various components of device 100.

Controller 104 may include one or more electronic components and/orsystems arranged to facilitate certain operations of device 100.Controller 104 may be disposed within device 100 in any feasible manner.In one embodiment, controller 104 may be disposed, at least partially,within a central cavity region of rotary link 122.

In some examples, controller 104 may include or otherwise be coupled towiring used for transfer of control signals to various components ofdevice 100 and/or for transfer of data from various components of device100 to controller 104. For example, the data that controller 104receives may include sensor data indicating detections of signals byreceiver 114, among other possibilities. Moreover, the control signalssent by controller 104 may operate various components of device 100,such as by controlling emission of signals by transmitter 106,controlling detection of signals by the receiver 114, and/or controllingactuator(s) 118 to rotate rotating platform 116, among otherpossibilities.

To that end, in some examples, controller 104 may include one or moreprocessors, data storage, and program instructions (stored on the datastorage) executable by the one or more processors to cause device 100 toperform the various operations described herein. The processor(s) maycomprise one or more general-purpose processors and/or one or morespecial-purpose processors. To the extent that controller 104 includesmore than one processor, such processors could work separately or incombination. The data storage, in turn, may comprise one or morevolatile and/or one or more non-volatile storage components, such asoptical, magnetic, and/or organic storage, and the data storage may beoptionally integrated in whole or in part with the processor(s).

In some instances, the controller may communicate with an externalcontroller or the like (e.g., a computing system arranged in a vehicleto which device 100 is mounted) so as to help facilitate transfer ofcontrol signals and/or data between the external controller and thevarious components of device 100.

Additionally or alternatively, in some examples, controller 104 mayinclude circuitry wired to perform one or more of the operationsdescribed herein. For example, controller 104 may include one or morepulser circuits that provide pulse timing signals for triggeringemission of pulses or other signals by transmitter 106. For instance,each pulser circuit may drive a respective emitter that provides one ormore beams arranged to scan one or more respective portions of the FOVof device 100.

Additionally or alternatively, in some examples, controller 104 mayinclude one or more special purpose processors, servos, or other typesof controllers. For example, controller 104 may include aproportional-integral-derivative (PID) controller or other control loopfeedback mechanism that operates actuator(s) 118 to cause the rotatingplatform to rotate at a particular frequency or phase. Other examplesare possible as well.

Transmitter 106 may be configured to transmit signals toward anenvironment of device 100. As shown, transmitter 106 may include one ormore emitters 140. Emitters 140 may include various types of emittersdepending on a configuration of device 100.

In a first example, where device 100 is configured as a LIDAR device,transmitter 106 may include one or more light emitters 140 that emit oneor more light beams and/or pulses having wavelengths within a wavelengthrange. The wavelength range could be, for example, in the ultraviolet,visible, and/or infrared portions of the electromagnetic spectrum. Insome examples, the wavelength range can be a narrow wavelength range,such as that provided by lasers. A non-exhaustive list of example lightemitters 140 includes laser diodes, diode bars, light emitting diodes(LED), vertical cavity surface emitting lasers (VCSEL), organic lightemitting diodes (OLED), polymer light emitting diodes (PLED), lightemitting polymers (LEP), liquid crystal displays (LCD),microelectromechanical systems (MEMS), fiber lasers, and/or any otherdevice configured to selectively transmit, reflect, and/or emit light toprovide a plurality of emitted light beams and/or pulses.

In a second example, where device 100 is configured as an activeinfrared (IR) camera, transmitter 106 may include one or more emitters140 configured to emit IR radiation to illuminate a scene. To that end,transmitter 106 may include any type of emitter (e.g., light source,etc.) configured to provide the IR radiation.

In a third example, where device 100 is configured as a RADAR device,transmitter 106 may include one or more antennas , waveguides, and/orother type of RADAR signal emitters 140, that are configured to emitand/or direct modulated radio-frequency (RF) signals toward anenvironment of device 100.

In a fourth example, where device 100 is configured as a SONAR device,transmitter 106 may include one or more acoustic transducers, such aspiezoelectric transducers, magnetostrictive transducers, electrostatictransducers, and/or other types of SONAR signal emitters 140, that areconfigured to emit a modulated sound signal toward an environment ofdevice 100. In some implementations, the acoustic transducers can beconfigured to emit sound signals within a particular wavelength range(e.g., infrasonic, ultrasonic, etc.). Other examples are possible aswell.

In some implementations, device 100 (and/or transmitter 106) can beconfigured to emit a plurality of signals (e.g., light beams, IRsignals, RF waves, sound waves, etc.) in a relative spatial arrangementthat defines a FOV of device 100. For example, each beam (or signal) maybe configured to propagate toward a portion of the FOV. In this example,multiple adjacent (and/or partially overlapping) beams may be directedto scan multiple respective portions of the FOV during a scan operationperformed by device 100. Other examples are possible as well.

To that end, optical element(s) 108 can be optionally included in orotherwise coupled to transmitter 106 and/or receiver 114. In oneexample, optical element(s) 108 can be arranged to direct light fromlight sources or emitters in transmitter 106 toward the environment. Inanother example, optical element(s) 108 can be arranged to focus lightfrom the environment toward receiver 114. As such, optical element(s)108 may include any feasible combination of mirror(s), waveguide(s),lens(es), or other types optical components, that are arranged to guidepropagation of light through physical space and/or to adjust certaincharacteristics of the light.

Receiver 114 may include one or more detectors 110 configured to detectreflections of the signals emitted by transmitter 106.

In a first example, where device 100 is configured as a RADAR device,receiver 114 may include one or more antennas (i.e., detectors 110)configured to detect reflections of the RF signal transmitted bytransmitter 106. To that end, in some implementations, the one or moreantennas of transmitter 106 and receiver 114 can be physicallyimplemented as the same physical antenna structures.

In a second example, where device 100 is configured as a SONAR device,receiver 114 may include one or more sound sensors 110 (e.g.,microphones, etc.) that are configured to detect reflections of thesound signals emitted by transmitter 106.

In a third example, where device 100 is configured as an active IRcamera, receiver 114 may include one or more light detectors 110 (e.g.,charge-coupled devices (CCDs), etc.) that are configured to detect asource wavelength of IR light transmitted by transmitter 106 andreflected off a scene toward receiver 114.

In a fourth example, where device 100 is configured as a LIDAR device,receiver 114 may include one or more light detectors 110 (e.g.,photodiodes, avalanche photodiodes, etc.) that are arranged to interceptand detect reflections of the light pulses or beams emitted bytransmitter 106 (and reflected from one or more objects in theenvironment of device 100). To that end, receiver 114 may be configuredto detect light having wavelengths in the same wavelength range as thelight emitted by transmitter 106. In this way, for instance, device 100may distinguish reflected light pulses originated by device 100 fromother light in the environment.

In some implementations, receiver 114 may include a photodetector array,which may include one or more detectors configured to convert detectedlight into an electrical signal indicating a measurement of the detectedlight. The photodetector array could be arranged in a variety ways. Forinstance, the detectors can be disposed on one or more substrates (e.g.,printed circuit boards (PCBs), flexible PCBs, etc.) and arranged todetect incoming light that is traveling along an optical path of anoptical lens of device 100 (e.g., optical element(s) 108). Also, such aphotodetector array could include any feasible number of detectorsaligned in any feasible manner. Additionally, the detectors in the arraymay take various forms. For instance, the detectors may take the form ofphotodiodes, avalanche photodiodes (APDs), silicon photomultipliers(SiPMs), single photon avalanche diodes (SPADs), multi-pixel photoncounters (MPPCs), phototransistors, cameras, active pixel sensors (APS),charge coupled devices (CCD), cryogenic detectors, and/or any othersensor of light configured to receive focused light having wavelengthsin the wavelength range of the emitted light.

In some examples, device 100 can select or adjust a horizontal scanningresolution by changing a rate of rotation of device 100 (and/ortransmitter 106 and receiver 114). Additionally or alternatively, thehorizontal scanning resolution can be modified by adjusting a pulse rateof signals emitted by transmitter 106. In a first example, transmitter106 may be configured to emit pulses at a pulse rate of 15,650 pulsesper second, and to rotate at 10 Hz (i.e., ten complete 360° rotationsper second) while emitting the pulses. In this example, receiver 114 mayhave a 0.23° horizontal angular resolution (e.g., horizontal angularseparation between consecutive pulses). In a second example, if device100 is instead rotated at 20 Hz while maintaining the pulse rate of15,650 pulses per second, then the horizontal angular resolution maybecome 0.46°. In a third example, if transmitter 106 emits the pulses ata rate of 31,300 pulses per second while maintaining the rate ofrotation of 10 Hz, then the horizontal angular resolution may become0.115°. In some examples, device 100 can be alternatively configured toscan a particular range of views within less than a complete 360°rotation of device 100. Other implementations are possible as well.

It is noted that the pulse rates, angular resolutions, rates ofrotation, and viewing ranges described above are only for the sake ofexample, and thus each of these scanning characteristics could varyaccording to various applications of device 100.

Rotating platform 116 may be configured to rotate about an axis. To thatend, rotating platform 116 can be formed from any solid materialsuitable for supporting one or more components mounted thereon. Forexample, transmitter 106 and receiver 114 may be arranged on rotatingplatform 116 such that each of these components moves relative to theenvironment based on rotation of rotating platform 116. In particular,these components could be rotated about an axis so that device 100 mayobtain information from various directions. In this manner, a pointingdirection of device 100 can be adjusted horizontally by actuating therotating platform 114 to adjust a FOV of device 100 in variousdirections.

In order to rotate platform 116 in this manner, one or more actuators118 may actuate the rotating platform 114. To that end, actuators 118may include motors, pneumatic actuators, hydraulic pistons, and/orpiezoelectric actuators, among other possibilities.

With this arrangement, controller 104 could operate actuator 118 torotate rotating platform 116 in various ways so as to obtain informationabout the environment. In one example, rotating platform 116 could berotated in either direction. In another example, rotating platform 116may carry out complete revolutions such that device 100 scans a 360°view of the environment. Moreover, rotating platform 116 could rotate atvarious frequencies so as to cause device 100 to scan the environment atvarious refresh rates. In one embodiment, device 100 may be configuredto have a refresh rate of 10 Hz (e.g., ten complete rotations of device100 per second). Other refresh rates are possible.

Alternatively or additionally, device 100 may be configured to adjustthe pointing direction of an emitted signal (emitted by transmitter 106)in various ways. In one implementation, signal emitters (e.g., lightsources, antennas, acoustic transducers, etc.) of transmitter 106 can beoperated according to a phased array configuration or other type of beamsteering configuration.

In a first example, where device 100 is configured as a LIDAR device,light sources or emitters in transmitter 106 can be coupled to phasedarray optics that control the phase of light waves emitted by the lightsources. For instance, controller 104 can be configured to adjust thephased array optics (e.g., phased array beam steering) to change theeffective pointing direction of a light signal emitted by transmitter106 (e.g., even if rotating platform 116 is not rotating).

In a second example, where device 100 is configured as a RADAR device,transmitter 106 may include an array of antennas, and controller 104 canprovide respective phase-shifted control signals for each individualantenna in the array to modify a pointing direction of a combined RFsignal from the array (e.g., phased array beam steering).

In a third example, where device 100 is configured as a SONAR device,transmitter 106 may include an array of acoustic transducers, andcontroller 104 can similarly operate the array of acoustic transducers(e.g., via phase-shifted control signals, phased array beam steering,etc.) to achieve a target pointing direction of a combined sound signalemitted by the array (e.g., even if rotating platform 116 is notrotating, etc.).

Stationary platform 120 may take on any shape or form and may beconfigured for coupling to various structures, such as to a top of avehicle, a robotic platform, assembly line machine, or any other systemthat employs device 100 to scan its surrounding environment, forexample. Also, the coupling of the stationary platform may be carriedout via any feasible connector arrangement (e.g., bolts, screws, etc.).

Rotary link 122 directly or indirectly couples stationary platform 120to rotating platform 116. To that end, rotary link 122 may take on anyshape, form and material that provides for rotation of rotating platform116 about an axis relative to the stationary platform 120. For instance,rotary link 122 may take the form of a shaft or the like that rotatesbased on actuation from actuator 118, thereby transferring mechanicalforces from actuator 118 to rotating platform 116. In oneimplementation, rotary link 122 may have a central cavity in which oneor more components of device 100 may be disposed. In some examples,rotary link 122 may also provide a communication link for transferringdata and/or instructions between stationary platform 120 and rotatingplatform 116 (and/or components thereon such as transmitter 106 andreceiver 114).

Housing 124 may take on any shape, form, and material and may beconfigured to house one or more components of device 100. In oneexample, housing 124 can be a dome-shaped housing. Further, in someexamples, housing 124 may be composed of a material that is at leastpartially non-transparent, which may allow for blocking of at least somesignals from entering the interior space of the housing 124 and thushelp mitigate thermal and noise effects of ambient signals on one ormore components of device 100. Other configurations of housing 124 arepossible as well.

In some examples, housing 124 may be coupled to rotating platform 116such that housing 124 is configured to rotate based on rotation ofrotating platform 116. In these examples, transmitter 106, receiver 114,and possibly other components of device 100 may each be disposed withinhousing 124. In this manner, transmitter 106 and receiver 114 may rotatealong with housing 124 while being disposed within housing 124. In otherexamples, housing 124 may be coupled to stationary platform 120 or otherstructure such that housing 124 does not rotate with the othercomponents rotated by rotating platform 116.

It is noted that this arrangement of device 100 is described forexemplary purposes only and is not meant to be limiting. As noted above,in some examples, device 100 can be alternatively implemented with fewercomponents than those shown. In one example, device 100 can beimplemented without rotating platform 100. For instance, transmitter 106can be configured to transmit a plurality of signals spatially arrangedto define a particular FOV of device 100 (e.g., horizontally andvertically) without necessarily rotating transmitter 106 and receiver114. Other examples are possible as well.

FIG. 2 illustrates a LIDAR device 200, according to an exampleembodiment. In some examples, LIDAR 200 may be similar to device 100.For example, as shown, LIDAR device 200 includes a lens 208, a rotatingplatform 216, a stationary platform 220, and a housing 224 which may besimilar, respectively, to optical element 108, rotating platform 216,stationary platform 120, and housing 124. In the scenario shown, lightbeams 280 emitted by LIDAR device 200 may propagate from lens 108 alonga viewing (or pointing) direction of LIDAR 200 toward a FOV of LIDAR200, and may then reflect off one or more objects in the environment asreflected light 290.

In some examples, housing 224 can be configured to have a substantiallycylindrical shape and to rotate about an axis of LIDAR device 200. Inone example, housing 224 can have a diameter of approximately 10centimeters. Other examples are possible. In some examples, the axis ofrotation of LIDAR device 200 is substantially vertical. For instance, athree-dimensional map of a 360-degree view of the environment of LIDARdevice 200 can be determined by rotating housing 224 about a verticalaxis. Additionally or alternatively, in some examples, LIDAR device 200can be configured to tilt the axis of rotation of housing 224 to controla field of view of LIDAR device 200. Thus, in some examples, rotatingplatform 216 may comprise a movable platform that may tilt in one ormore directions to change the axis of rotation of LIDAR device 200.

In some examples, lens 208 can have an optical power to both collimate(and/or direct) emitted light beams 280 toward the environment of device200, and to focus reflected light 290 from one or more objects in theenvironment of LIDAR device 200 onto detectors in LIDAR device 200. Inone example, lens 208 has a focal length of approximately 120 mm. Otherexamples are possible. By using the same lens 208 to perform both ofthese functions, instead of a transmit lens for collimating and areceive lens for focusing, advantages with respect to size, cost, and/orcomplexity can be provided.

In other examples, instead of the single lens 208 configuration as shownin FIG. 2, LIDAR 200 could be alternatively implemented to includeseparate transmit lens (for manipulating emitted light 280) and receivelens (for focusing reflected light 290).

FIG. 3 illustrates a cross-section view of a plurality of emitted beams,exemplified by beams 302, 304, 306, 308, 312, 318, that are spatiallyarranged to scan respective portions of a FOV 300, according to exampleembodiments.

FOV 300 may correspond to a FOV that is illuminated bytransmitter(s)/emitter(s) (e.g., transmitter 106, emitter(s) 140, etc.)of an active sensor (e.g., devices 100, 200) during a scan of the FOV.

For example, referring back to FIG. 2, FOV 300 may correspond to theregion of the environment of device 200 toward which light beams 280 areemitted. In this example, the beams shown in FIG. 3 may be propagatingthrough the page in the direction of the arrow 280 shown in FIG. 2.

In some examples, a device or system herein may transmit the pluralityof beams 302, 304, 306, 308, 312, 318, etc., in a relative spatialarrangement such as the arrangement shown in FIG. 3, during an emissiontime period of a particular scan of FOV 300. Thus, as shown, each of theemitted beams may scan a respective portion of FOV 300. For example,beam 302 may have a particular (elevational and azimuthal) angularposition within the spatial arrangement of the plurality of beams shown.In a LIDAR device configuration for instance, the particular angularposition of beam 302 may be defined by one or more optical elements(e.g., lenses, apertures, waveguides, etc.) that direct beam 302 in aparticular transmit path. Thus, for instance, the various respectiveportions of FOV 300 scanned by the emitted beams may together define thevertical and horizontal extents of FOV 300 that are scanned by multiplechannels of an active sensor.

In some examples, where a device performs a sequence of scans of FOV300, the device can then perform a second scan of FOV 300 bytransmitting a second plurality of beams, in a similar spatialarrangement as that shown for the beams of FIG. 3, to scan therespective portions of FOV 300 another time, and so on.

In some examples, a device herein may include a plurality of emitters(e.g., emitters 140) that emit the plurality of beams shown in FIG. 3. Afirst emitter of the plurality may emit signals toward a first portionof FOV 300, and a second emitter may emit light that illuminates asecond portion of FOV 300. In a first example, the first emitter may becoupled to optical elements (e.g., waveguide(s), aperture(s), lens(es),etc.) that direct its emitted light to the angular position of beam 302in the spatial arrangement of the emitted beams. Similarly, in thisexample, signals emitted by the second emitter may be directed to theangular position of 312, and so on. In a second example, the signalsfrom each emitter may be split into multiple beams. For instance,signals from the first emitter can be split into the row of beamsincluding beams 302, 304, 306, 308. Similarly, for instance, signalsfrom the second emitter may be split to provide the row of four beamsincluding beams 312 and 318. Other examples are possible.

In some examples, a device herein may include a plurality of detectorsfor receiving reflected signals (e.g., light) from respective portionsof FOV 300 illuminated by beams 302, 304, 306, 308, 312, 318, etc.Referring back to FIG. 2 for example, lens 208 may be configured tofocus received light 290 for receipt by a plurality of detectors (e.g.,detectors 110 of device 100). Moreover, referring back to FIG. 1, afirst detector of detectors 110 can be arranged to receive a firstportion of the focused light that includes a reflection of beam 302, asecond detector of detectors 110 can be arranged to receive a secondportion of the focused light that includes a reflection of beam 304, andso on.

It is noted that the arrangement, shapes, and/or number of the pluralityof emitted beams shown in FIG. 3 may vary, and are only illustrated asshown for convenience in description. For example, FOV 300 could bescanned by an example device herein that emits more or fewer beams forscanning various respective portions of FOV 300. As another example, thebeams can be arranged in a different spatial arrangement (e.g., circulararrangement, linear arrangement, grid arrangement, etc.) than thearrangement shown in FIG. 3.

III. Example Methods

FIG. 4 is a flowchart of a method 400, according to example embodiments.Method 400 presents an embodiment of a method that could be used withany of devices 100 and/or 200, for example. Method 400 may include oneor more operations, functions, or actions as illustrated by one or moreof blocks 402-404. Although the blocks are illustrated in a sequentialorder, these blocks may in some instances be performed in parallel,and/or in a different order than those described herein. Also, thevarious blocks may be combined into fewer blocks, divided intoadditional blocks, and/or removed based upon the desired implementation.

In addition, for method 400 and other processes and methods disclosedherein, the flowchart shows functionality and operation of one possibleimplementation of present embodiments. In this regard, each block mayrepresent a module, a segment, a portion of a manufacturing or operationprocess, or a portion of program code, which includes one or moreinstructions executable by a processor for implementing specific logicalfunctions or steps in the process. The program code may be stored on anytype of computer readable medium, for example, such as a storage deviceincluding a disk or hard drive. The computer readable medium may includea non-transitory computer readable medium, for example, such ascomputer-readable media that stores data for short periods of time likeregister memory, processor cache and Random Access Memory (RAM). Thecomputer readable medium may also include non-transitory media, such assecondary or persistent long term storage, like read only memory (ROM),optical or magnetic disks, compact-disc read only memory (CD-ROM), forexample. The computer readable media may also be any other volatile ornon-volatile storage systems. The computer readable medium may beconsidered a computer readable storage medium, for example, or atangible storage device.

In addition, for method 400 and other processes and methods disclosedherein, each block in FIG. 4 may represent circuitry that is wired toperform the specific logical functions in the process.

At block 402, method 400 involves causing a plurality of emitters toemit a plurality of light pulses during a first emission time periodassociated with a first scan of a field-of-view (FOV). The plurality ofemitters may include at least a first emitter and a second emitter. Thefirst emitter may be configured to illuminate a first portion of theFOV, and the second emitter may be configured to illuminate a secondportion of the FOV.

Referring back to FIG. 3 for example, a first emitter (e.g., one ofemitters 140 of device 100, etc.) may emit light that includes a firstrow of light beams 302, 304, 306, 308 to scan a first portion of FOV 300illuminated by the first row. Further, a second emitter (e.g., anotherone of emitters 140, etc.) may emit light that includes a second row oflight beams (e.g., including beams 312, 318 and the two beams inbetween) to scan a second portion of FOV 300 illuminated by the secondrow, and so on.

In some implementations, method 400 involves obtaining the first scan ofthe FOV, where obtaining the first scan involves causing each emitter ofthe plurality of emitters to emit a respective light pulse during thefirst emission time period. For example, the first emission time periodmay have a start time (e.g., t=0 ns) and an end time (e.g., t=499 ns),and each emitter of the plurality of emitters may be coupled to arespective pulser circuit (e.g., controller 140) that triggers emissionof a respective light pulse by the emitter during a time offset betweenthe start time and end time of the first emission time period. In oneembodiment, a first pulser circuit can be configured to trigger pulseemissions by two or more particular emitters of the plurality ofemitters. For instance, the two or more emitters may be configured toemit respective light pulses at a same time offset within the firstemission time period. In another embodiment, the first pulser circuitcan be configured to trigger pulse emissions by one emitter and a secondpulser circuit can be configured to trigger emissions by anotheremitter.

Thus, in some implementations, method 400 involves causing a firstemitter (of the plurality of emitters) to emit a first-emitter lightpulse at a first-emitter time offset from the start time (or the endtime) of the first emission time period, and causing a second emitter toemit a second-emitter light pulse at a second-emitter time offset fromthe start time (or the end time) of the first emission time period. Inan example scenario, where the first emission time period extends fromt=0 ns to t=499 ns, the first emitter can be configured to emit a lightpulse at the first-emitter time offset of 0 ns from the start time(i.e., at t=0 ns) or from the end time (i.e., at t=499 ns) of the firstemission time period. Similarly, in this scenario, the second emittermay emit a light pulse at the second-emitter time offset of 10 ns fromthe start time (i.e., at t=10 ns) or from the end time (i.e., at t=489ns).

In some examples, the first-emitter light pulse (and/or thesecond-emitter light pulse) can be split into multiple light beams ofmultiple channels scanned by a system of method 400. Referring back toFIG. 3 for example, light from a single emitter (e.g., LED, etc.) may besplit (e.g., using mirrors, waveguides, beam splitters, etc.) into fourlight beams 302, 304, 306, 308 to scan four separate portions of FOV300. Alternatively or additionally, in some examples, the first-emitterlight pulse (and/or the second-emitter light pulse) can be transmittedas a single respective light beam toward the FOV. Referring back to FIG.3 for example, beam 302 can be emitted by the first emitter, beam 304can be emitted the second emitter, and so on. Other examples arepossible.

In some examples, a difference between the first-emitter time offset andthe second-emitter time offset may be at least 2.5 nanoseconds (oranother predetermined threshold). Referring back to FIG. 3 for example,an emission time of beam 302 can be separated from an emission time ofbeam 304 (and/or any other beam) by at least a threshold amount of time(e.g., 2.5 nanoseconds). In some examples, the emitter-specific timeoffsets assigned to each of the plurality of emitters can be separatedby multiples of the predetermined threshold (e.g., the first emitter canbe assigned a first-emitter time offset value of 1*2.5=2.5 ns, thesecond emitter can be assigned a second-emitter time offset value of10*2.5=25 ns, etc.).

At block 404, method 400 involves obtaining the first scan based onmeasurements of light from the FOV received during a first detectiontime period that begins after (or at) the end time of the first emissiontime period.

In an example scenario, the first emission time period may extend from astart time of t=0 ns to an end time of t=499 ns. In this scenario, thefirst detection time period may begin after the end time (e.g., at t=500ns) or at the end time (i.e., at t=499 ns) of the first emission timeperiod. Referring back to FIG. 3 for instance, a system of method 400may transmit light beams 302, 304, 306, 308 at respective time offsets(e.g., at t=0 ns, t=100 ns, t=200 ns, and t=400 ns) within the firstemission time period. Further, the system may then obtain the firstmeasurement of light incident on detectors 110 (shown in FIG. 1) duringthe first detection time period (e.g., from t=500 ns to t=2500 ns).Thus, in some examples, the measurements of light from the FOV at block404 may include one or more measurements of incident light associatedwith one or more channels that illuminate one or more respectiveportions of the FOV. For example, the measurements of the light from theFOV can be obtained by a plurality of detectors (e.g., detectors 110),where each detector of the plurality is aligned with a respectiveportion of the FOV illuminated by a respective light pulse of theplurality of light pulses.

In some implementations, method 400 involves obtaining a sequence ofscans of the FOV including at least the first scan and a second scansubsequent to the first scan. For instance, consider a scenario wherethe first scan has a first emission time period from a start time of t=0ns to an end time of t=499 ns, and a first detection time period fromt=500 ns to t=2500 ns. In this scenario, the second scan may have asecond emission time period that begins at a start time of t=5000 ns andends at an end time of t=5499 ns, and a second detection time periodfrom t=5500 ns to t=7500 ns. In this scenario, a device of method 400may be configured to obtain a scan of the FOV every 5000 ns. Referringback to FIG. 3 for instance, the device may be configured to emit all ofthe plurality of beams shown to illuminate FOV 300 during the firstemission time period, and then a second similar plurality of beamsduring the second emission time period.

In some implementations, method 400 involves illuminating the firstportion of the FOV using the first emitter during the first scan, andilluminating a different portion of the FOV using the first emitterduring the second scan. Referring back to FIG. 1 for example,transmitter 106 (and/or optical element 108) can be configured to adjustthe source (e.g., emitter A of emitters 140, emitter B of emitters 140,etc.) of light beams 302, 304, 306, 308, 312, 318, etc. For instance,device 100 may include mirrors, switches, actuators, and/or any othertype of circuitry to allow controlling which portions of the scanned FOVare illuminated by which emitter during a particular scan. In thisexample, during the first scan, beam 302 could be emitted by the firstemitter to illuminate the first portion of FOV 300. In this example,during the second scan, beam 304 could be emitted by the first emitterinstead of beam 302 to illuminate a different portion of the FOV, and soon. Similarly, the scanning channel(s) illuminated by the second emitter(and/or any other emitter of the plurality of emitters) can be changedbetween successive scans of the FOV.

Thus, in these implementations, a mapping between emitters and scanningchannels can be varied to dither the relative emission times of pulsesduring consecutive scans of the FOV. By way of example, referring backto FIG. 3, pulse 302 during the first scan can be emitted by the firstemitter at the first-emitter time offset from the start time (or endtime) of the first emission time period, then another pulse 302 can beemitted by the second emitter at the second-emitter time offset from thestart time (or end time) of the second emission time period, and so on.

Alternatively or additionally, in some implementations, method 400 mayinvolve modifying the first-emitter time offset for the second scan. Inthese implementations, obtaining the second scan described above maycomprise causing the first emitter to emit another first-emitter lightpulse at the modified first-emitter time offset (from a start time orend time) of the second emission time period associated with the secondscan. In the scenario above for instance, a first-emitter time offset of0 ns may be used for the first emitter during the first scan (e.g.,first-emitter light pulse emitted at t 32 0 ns if the first-emitteroffset is from the start time, or at t=499 ns if the first-emitteroffset is from the end time). Further, in this scenario, thefirst-emitter time offset may then be adjusted to 50 ns for the secondscan. For instance, another first-emitter light pulse emitted during thesecond scan may be emitted at t=5000+50=5050 ns (offset from start timeof second emission time period), or at t=5500−50=5450 ns (offset fromend time of second emission time period. Further, in some examples,similarly to the first scan, obtaining the second scan may be based onmeasurements of light from the FOV received by the plurality ofdetectors (e.g., detectors 110) during the second detection time periodthat begins after (or at) the end time of the second emission timeperiod.

In some implementations, method 400 may also involve modifying thesecond-emitter time offset for the second scan. In theseimplementations, obtaining the second scan may also involve causing thesecond emitter to emit another second-emitter light pulse at themodified second-emitter time offset from the start time (or the endtime) of the second emission time period. For instance, similarly to thediscussion above for the modification of the first-emitter time offset,the second-emitter offset can be adjusted for each successive scan inthe sequence.

In some implementations, method 400 involves determining a pseudo-randomtime offset sequence. For example, controller 104 (or another externalcomputing system) can be configured to generate a sequence of timeoffsets within a typical emission period (e.g., between 0 and 499 ns,etc.) for a certain number of scans of the FOV by a particular emitter(e.g., 50 offsets for 50 pulse emissions by a first emitter during 50consecutive scan periods, etc.) of emitters 140. In some examples, thesequence of pseudo-random time offsets may be computed as random timeoffset values within a particular range (e.g., 0 to 499 ns, etc.).Additionally or alternatively, in some examples, the values of the timeoffsets in the sequence can be selected from the particular rangeaccording to one or more rules (e.g., to constrain the extent of theirrandomness).

In a first example, the time offsets in the sequence can be selected tobe non-repeatable. For instance, the first emitter can be assigned aspecific number (e.g., 50, 60, etc.) of unique time offset values forthe same number (e.g., 50, 60, etc.) of consecutive scans of the FOV(i.e., the sequence of scans). Accordingly, in some implementations,determining the pseudo-random time offset sequence may comprisedetermining a sequence of time offset values that are different from oneanother. With this arrangement for instance, a system of method 400 canprevent (or reduce the likelihood of) the first emitter being assignedthe same time offset value randomly (at least for a particular number ofconsecutive scans).

In a second example, the time offsets in the sequence can be selected tobe different from corresponding time offsets assigned to other emittersof the LIDAR device during a same scan of the FOV. For instance, acomputing device of method 400 may pre-compute a plurality ofpseudo-random time offset sequences for use with the plurality ofemitters during the sequence of scans. The respective time offset valuesordered at a same position in each sequence can be selected to bedifferent from one another. For instance, consider a scenario where afirst time offset sequence is generated to include the time offsets of 0ns, 100 ns, 50 ns (in that order). In this scenario, every othersequence may be generated to include a first time offset different than0 ns, a second time offset different than 100 ns, a third time offsetdifferent than 50 ns, and so on. Thus, in this example, a system ofmethod 400 can provide a different time offset value for each emitter ofthe LIDAR device during any particular scan of the sequence of scans byassigning the first pseudo-random time offset sequence to the firstemitter, a second pseudo-random time offset sequence to the secondemitter, and so on.

Accordingly, in some implementations, method 400 may involve determininga plurality of pseudo-random time offset sequences for the plurality ofemitters. In these implementations, a given time offset of a givensequence may have a different value than corresponding time offsetshaving a same order-position in other sequences of the plurality ofpseudo-random time offset sequences.

Due to the varying of the relative emission times of the plurality ofemitters within the respective emission time periods of the sequence ofscans, a spurious signal received at a first detector aligned with afirst emitter (e.g., reflection of a light beam that was not emitted bythe first emitter) may correspond to a different distance in eachsuccessive scan of the sequence (e.g., incoherent detections of thespurious signal by the first detector). However, because the respectivedetection time period of each scan begins after the respective emissiontime period of the scan ends, a minimum range measured by each detectormay also vary in each scan of the sequence.

For example, consider a scenario where the first emission time period ofthe first scan is between t=0 ns and t=500 ns, the first detection timeperiod of the first scan is between t=500 ns and t=2500 ns, the secondemission time period of the second scan is between t=5000 ns and t=5500ns, and the second detection time period of the second scan is betweent=5500 ns and t=7500 ns. In this scenario, the first emitter may emit afirst-emitter light pulse in the first scan at t=500 ns (i.e.,first-emitter time offset is 0 ns from the end time of the firstemission time period). Thus, during the first scan, the first detectoraligned with the first emitter may begin detecting reflections of thefirst-emitter light pulse as soon as it is emitted (i.e., at t=500 ns),and may thus detect an object that is 0 meters away from a LIDAR deviceof method 400. In this scenario, during the second scan of the FOV, thefirst-emitter time offset may be modified to 500 ns (e.g., anotherfirst-emitter light pulse is emitted 500 ns prior to the end time of thesecond emission time period or at t=5500−500=5000 ns). Thus, in thesecond scan, reflections of the (another) first-emitter light pulse thatarrive at the LIDAR device within 500 ns (i.e., between t=5000 ns andt=5500 ns) after the first-emitter light pulse is emitted might not bedetected by the first detector aligned with the first emitter. Morespecifically, in this scenario, reflections off objects that are 75meters or less from the LIDAR device might not be detected by the firstdetector because they would arrive before the second detection timeperiod of the second scan begins (i.e., before t=5500 ns).

Accordingly, in some examples, the randomness of the pseudo-random timeoffset sequence can be constrained to achieve a minimum scanning rangeby the first emitter at least once within a particular number ofconsecutive scans. For instance, the pseudo-random time offset sequencemay be constrained such that every 10 successive time offsets in thepseudo-random time offset sequence includes at least one time offset of0 ns (e.g., from the end time of the respective emission time period ofthe scan). With this arrangement, a particular channel of the LIDARdevice a may be configured to scan objects near the LIDAR device atleast once in every 10 scans in the sequence of scans. By way of anexample scenario, referring back to FIG. 3, a channel that scans theportion of FOV 300 illuminated by beam 302 may emit ten successive beams/ pulses similar to beam 302 during ten successive scans of FOV 300according to the pseudo-random time sequence. For this scenario, in atleast one of the ten scans, the respective emitted beam may be triggeredat the end of the respective emission time period of the at least onescan to ensure the portion of the FOV scanned by that channel can detectobjects at a 0 meter range at least once during the ten successivescans.

Similarly, in some examples, the randomness of the pseudo-random timeoffset sequence can be constrained to achieve multiple minimum scanningranges using the first emitter during the sequence of scans. Forexample, the time offset sequence may be generated to include at leastone time offset for a 0 meter minimum range, at least one time offsetfor a 10 meter minimum range, at least one offset for a 20 meter minimumrange, and so on.

Thus, in some implementations, determining the pseudo-random time offsetsequence may involve determining at least one time offset that is lessthan or equal to a predetermined threshold offset (e.g., <=0 ns, <=50ns, etc.). Additionally or alternatively, determining the pseudo-randomtime offset sequence may involve determining at least one time offsetthat is within a threshold predetermined threshold range (e.g., between95 ns and 105 ns, etc.).

In some implementations, method 400 may involve selecting thefirst-emitter time offset for each scan of the sequence of scans fromthe pseudo-random time offset sequence based on an order of the scan inthe sequence of scans. For example, a first time offset may be selectedfrom the pseudo-random time offset sequence for a first scan of thesequence of scans, a second time offset subsequent to the first offsetin the pseudo-random time offset sequence may be selected for a secondscan subsequent to the first scan in the sequence of scans, and so on.

In some examples, determining the pseudo-random time offset sequence mayinvolve obtaining a predetermined pseudo-random time offset sequence.For instance, the time offset sequences may be precomputed (e.g., by acontroller of the LIDAR device, or by another external computing system)and/or retrieved from data storage prior to obtaining a scan of theenvironment. In other examples however, determining the pseudo-randomtime offset sequence may alternatively involve generating thepseudo-random time offset sequence at any other time (e.g., betweenscans, during scans, etc.).

In some implementations, method 400 involves obtaining a first sequenceof scans (e.g., 50 scans) and a second sequence of scans (e.g., 50additional scans) subsequent to the first sequence of scans. In theseimplementations, method 400 may also involve adjusting thesecond-emitter time offset for one or more of the second sequence ofscans according to the determined pseudo-random time offset sequence.For example, in line with the discussion above, the pseudo-random timeoffset sequence may be used to adjust the respective first-emitter timeoffsets assigned to the first emitter during the first sequence ofscans. Then, during the second sequence of scans, the same pseudo-randomtime offset sequence can be re-used to instead modify the respectivesecond-emitter time offsets assigned to the second emitter during thesecond sequence of scans. By doing so for instance, additionalrandomization of the light pulse emissions by the channels can beachieved as compared to implementations where the same pseudo-randomoffset sequence for every sequence of scans by a particular channel.

Referring back to FIG. 3 for example, a first emitter that illuminatesthe portion of FOV 300 illuminated by the row of beams 302, 304, 306,308 can be assigned a particular pseudo-random time offset sequence fora first sequence of N scans. Then, during a subsequent sequence of Nadditional scans, a different portion of the FOV illuminated by the rowof beams 312, 318 (and the three other beams in between) can be assignedthe particular pseudo-random time offset sequence (which was previouslyused with the first emitter), and so on.

In other implementations however, a same pseudo-random time offsetsequence can be alternatively re-used with the first emitter during boththe first sequence of scans and the second subsequent sequence of scans.

In some implementations, method 400 may involve illuminating a firstportion of the FOV using the first emitter during the first sequence ofscans, and illuminating a second portion of the FOV using the firstemitter during the second sequence of scans subsequent to the firstsequence of scans. Thus, referring now to FIG. 3 for example, the firstemitter can be configured to illuminate the portions of FOV 300corresponding to beams 302 and 304 during a first sequence of scans(e.g., 50 scans), and then the first emitter can be configured toilluminate the portion of the FOV corresponding to beams 308 and 318during a second subsequent sequence of scans (e.g., the next 50 scans),and so on. With this arrangement for instance, even if a samepseudo-random time offset sequence is re-used with the first emitterduring consecutive sequences of scans, a particular channel (e.g.,portion of FOV associated with beam 302) may effectively be scannedaccording to a different pseudo-random time offset sequence of thesecond emitter during the second sequence of scans.

In some implementations, method 400 involves determining, based on thefirst measurement of block 404, respective distances between a device ofmethod 400 and objects in the FOV illuminated by the plurality of beams.For instance, in an implementation where device 100 illuminates FOV 300,controller 104 may be configured to compute a time difference between anemission time of beam 302 (shown in FIG. 3) and a detection time of areflection of beam 302 (e.g., by receiver 114), and then compute thedistance between device 100 and an object within the portion of the FOVilluminated by beam 302 based on the time difference.

In some implementations, method 400 involves determining that alikelihood of false signal detections by one or more detectors of theLIDAR device is greater than a threshold based on signal characteristicsof a first signal received by a first detector of the LIDAR device. Forexample, controller 104 may receive a measurement of the first signalfrom the first detector, and then determine that the first signal has asignal intensity outside a given range (e.g., greater than an expectedintensity, a threshold high intensity expected when a retroreflector isilluminated by an emitter of the plurality of emitters, etc.). In thisexample, the one or more detectors (e.g., of other transmit/receivechannels) may detect false (e.g., spurious) signals due to portions ofthe light associated with the first signal having sufficient power to bealso detected (spuriously) by the one or more detectors. Further, inthis example, the spurious signals at the one or more channels may bereceived at substantially the same time when the first signal wasreceived at the first channel.

Accordingly, in some implementations, method 400 may also involvestoring an indication of a time of receipt of the first signal. Forinstance, a computing device (e.g., controller 104, external computer,etc.) that processes LIDAR data from the LIDAR device may access thestored indication to identify the one or more signals detected by otherdetectors at (substantially) the same time when the first signal wasalso detected by the first detector. In this instance, the computingdevice may then remove the one or more signals (e.g., if they are deemedto correspond to spurious detections) from the LIDAR data, or keep theone or more signals (e.g., if they are deemed to correspond to truedetections).

Accordingly, in some implementations, method 400 may also involveidentifying one or more error signals detected by one or more detectorsof the LIDAR device based on signal characteristics of a given signaldetected by a given detector other than the one or more detectors.Further, in some implementations, the identification of the one or moreerror signals may be based on a comparison of detection times of the oneor more error signals and a detection time of the given signal.

In some examples, the portion of the FOV scanned by a particular LIDARchannel during a sequence of scans may correspond to different physicalregions in the environment of the LIDAR device. Referring back to FIG. 2for example, LIDAR 200 may be configured to rotate about an axis (e.g.,vertical axis, etc.) while obtaining the sequence of scans of theenvironment. In this example, the portion of the FOV scanned by a firstchannel of LIDAR 200 (e.g., a portion of the FOV illuminated by thefirst emitter of method 400 and observed by the first detector of method400, etc.) during a first scan (when LIDAR 200 is at a first angularposition about its axis of rotation) may correspond to a differentphysical region in the environment of LIDAR 200 than the region scannedby the first channel during a second scan (e.g., performed after LIDAR200 rotates to a second angular position about the axis). Referring backto FIG. 3 for example, beam 302 may point toward a first angulardirection (relative to the axis of rotation of the LIDAR) during thefirst scan, and toward a second angular direction during the secondscan. In a scenario where the LIDAR rotates in a counterclockwisedirection after the first scan for instance, beam 302 may move to theleft of its position shown in FIG. 3.

In some scenarios, where the LIDAR is rotating and the first channelilluminates a retroreflector in the environment for instance, varyingthe respective emitter time offsets during the respective emission timeperiods of the sequence of scans in accordance with method 400 couldstill result in incoherent distance measurements indicated by spurioussignals received in a second channel due to the retroreflectorilluminated by the first channel. For instance, the retroreflector(e.g., street sign) may have a sufficient spatial extent such thatmultiple light pulses emitted by the first channel (in the sequence ofscans) while the LIDAR is rotating would still reflect off portions ofthe retroreflector (and therefore cause a sequence of spuriousdetections in the second channel). Thus, the present method mayfacilitate identification of spurious signal detections (e.g., due tochannel cross-talk, presence of retroreflectors, etc.) even in somescenarios where the LIDAR is moving (e.g., rotating, etc.) whileobtaining the sequence of scans.

As noted above, in some examples, a device or system of method 400 mayinclude a plurality of detectors (e.g., detectors 110) arranged toreceive light from respective portions of the FOV illuminated by theplurality of emitters. For example, a first detector of the plurality ofdetectors can be arranged (e.g., aligned, etc.) to receive light fromthe first portion of the FOV illuminated by the first emitter. Forinstance, the first detector can be positioned at a location where alens or other optical element assembly (e.g., optical elements 108)focuses light from the first portion of the FOV toward the firstdetector.

To that end, in some implementations, method 400 may also involvedetecting, via the first detector, a first-detector light pulse at afirst detection time during the first detection time period, andassociating the first-detector light pulse with presence of aretroreflector in the first portion of the FOV illuminated by the firstemitter. In line with the discussion above, for instance, thefirst-detector light pulse may have a larger than expected amount ofenergy, or may be received at a same time one or more other light pulsesdetected by one or more other detectors, among other possibilities.

Thus, in one implementation, associating the first-detector light pulsewith presence of the retroreflector is based on at least an intensity ofthe first-detector light pulse being greater than a threshold intensity.For instance, retroreflectors may have a relatively larger effectivereflectivity than other types of reflectors. Thus, in this instance, ifthe intensity of the detected light pulse is more than an expectedintensity of light from a regular reflector, then the device of method400 may determine that the detected light pulse was reflected by aretroreflector. To that end, the threshold intensity may be selecteddepending on a variety of factors, such as the configuration and/orapplication of the device that performs method 400 (e.g., 50% of thepeak intensity of the first-emitter light pulse or any otherpredetermined value), for example.

Alternatively or additionally, in this implementation, method 400 mayinvolve determining the threshold intensity based on the first-emittertime offset and the first detection time. For example, the thresholdintensity can be adjusted depending on the difference between a firstemission time of the first-emitter light pulse and the first detectiontime. For instance, if the detected light pulse was reflected by a farobject (i.e., difference between the first emission time and the firstdetection time is relatively large), then the threshold intensity can bereduced because the expected intensity of a reflection from the farobject is lower than if the detected light pulse was reflected by anearer object (i.e., where the difference between the first emissiontime and the first detection time is relatively lower).

In some implementations, method 400 may also involve detecting, via asecond detector, a second-detector light pulse at a second detectiontime during the first detection time period of the first scan. Forexample, the second detector may be arranged to measure light from thesecond portion of the FOV illuminated by the second emitter. Thus, inthis example, a device of method 400 may compare the first detectiontime to the second detection time as a basis for determining presence ofa retroreflector. For instance, based on the comparison, the device maydetermine whether the detection of the second-detector light pulse bythe second detector was caused by: (i) the presence of a retroreflectorin the first portion of the FOV illuminated by the first emitter, (ii)or the presence of an object (e.g., regular reflector) in the secondportion of the FOV illuminated by the second emitter.

Accordingly, in a first implementation, method 400 may involveassociating the second-detector light pulse with the presence of theretroreflector in the first portion of the FOV based on at least thefirst detection time being within a predetermined threshold to thesecond detection time. In a second implementation, method 400 mayinvolve associating the second-detector light pulse with presence of anobject in the second portion of the FOV based on a difference betweenthe first detection time and the second detection time being greaterthan the predetermined threshold.

For instance, if the first-detector light pulse and the second-detectorlight pulse were detected at same (or substantially similar) times, thena device of method 400 may determine that detection of thesecond-detector light pulse (e.g., “ghost” detection, etc.) was causedby the presence of the retroreflector in the first portion of the FOVilluminated by the first emitter. Whereas, for instance, if thefirst-detector light pulse and the second-detector light pulse weredetected at substantially different times, then the device may determinethat the second-detector light pulse was caused by light from the secondportion of the FOV illuminated by the second emitter.

To that end, the value of the predetermined threshold may depend on avariety of factors, such as error tolerances in the timing, delay,analog-to-digital data conversion times, optical assembly distortions(e.g., delays caused by receive optics such as lens, mirrors, etc.), orany other variable that affects the accuracy of the detection timesmeasured for signals from the first detector and the second detector. Inone embodiment, the predetermined threshold may be 0 nanoseconds. Forinstance, the device of method 400 may determine that thesecond-detector light pulse is associated with the presence of theretroreflector in response to the first detector time and the seconddetector time corresponding to a same detection time. In anotherembodiment, the predetermined threshold may be 0.1 nanoseconds (ns), 0.2ns, 0.3 ns, 0.4 ns, or any other value that would account for potentialerrors in measuring the detection times of the first-detector lightpulse and/or the second-detector light pulse.

FIG. 5 is a flowchart of another method 500, according to exampleembodiments. Method 500 presents an embodiment of a method that could beused with any of devices 100 and/or 200, for example. Method 500 mayinclude one or more operations, functions, or actions as illustrated byone or more of blocks 502-504. Although the blocks are illustrated in asequential order, these blocks may in some instances be performed inparallel, and/or in a different order than those described herein. Also,the various blocks may be combined into fewer blocks, divided intoadditional blocks, and/or removed based upon the desired implementation.

At block 502, method 500 involves transmitting a first plurality ofbeams toward respective portions of a field-of-view (FOV) during a firstemission time period associated with a first scan of the FOV. Referringback to FIG. 3 for example, a LIDAR transmitter may transmit theplurality of light beams 302, 304, 306, 308, 312, 318, etc., that arespatially arranged to illuminate respective portions of FOV 300. Forinstance, transmitter 106 (of device 100) may emit the first pluralityof light beams in a particular spatial arrangement (e.g., spatialarrangement of the beams shown in FIG. 3, etc.).

In some implementations, method 500 also involves transmitting a secondplurality of beams to illuminate the respective portions of the FOVduring a second emission time period associated with a second scan ofthe FOV. Continuing with the example of FIG. 3, a device of method 500may emit the plurality of light beams 302, 304, 306, 308, 312, 318,etc., shown in FIG. 3 during the first scan of FOV 300. In this example,the device may then emit the second plurality of beams (in a similarspatial arrangement) during the second scan of FOV 300.

At block 504, method 500 involves illuminating a first portion of theFOV at a first-portion time offset, and a second portion of the FOV at asecond-portion time offset. Referring back to FIG. 3 for example, beams302 and 304 may correspond to the first portion of the FOV illuminatedat a the first-portion time offset (e.g., t=100 ns) from a start time(or end time) of the first emission time period, and beams 306 and 308may correspond to the second portion of the FOV illuminated at thesecond-portion time offset (e.g., t=200 ns) from the start time (or endtime) of the first emission time period. Thus, continuing with theexample of FIG. 3, transmitter 106 (of device 100) may be configured toemit a first light beam (e.g., beam 302) of the first plurality of lightbeams toward a first portion of the FOV at the first-portion timeoffset, and a second light beam (e.g., beam 306) of the first pluralityof light beams toward the second portion of the FOV at thesecond-portion time offset.

In some implementations, method 500 may also involve illuminating thefirst portion of the FOV at a modified first-portion time offset from astart time (or end time) of a second emission time period of a secondscan of the FOV (after the first scan). In line with the discussionabove for instance, the modified first-portion time offset (e.g., 100ns) may thus be different from the first-portion time offset (e.g., 400ns) associated with the first scan. Continuing with the example of FIG.3, transmitter 106 may be configured to emit (during the second emissiontime period) a second plurality of light beams in the same spatialarrangement shown in FIG. 3, but while using different time offsetsbetween the emission times of the beams (than the time offsets usedbetween the emission times of the beams in the first scan). Forinstance, a third light beam of the second plurality of light beams maybe similar to beam 302 (e.g., at a same position in the spatialarrangement of the beams) but at the modified first-portion time offsetfrom a start time of the second emission time period as compared to thefirst-portion time offset used for emitting beam 302 during the firstscan.

Thus, in some implementations, method 500 may involve emitting the firstplurality of light beams (associated with the first scan) in aparticular spatial arrangement, and emitting the second plurality oflight beams (associated with the second scan) in the (same) particularspatial arrangement. For example, during the first scan, a first lightbeam (e.g., beam 302) of the first plurality of light beams (of thefirst scan) may have a first position in the particular spatialarrangement, and a second light beam (e.g., beam 306) of the firstplurality of light beams may have a second position in the particularspatial arrangement. Further, during the second scan or example, a thirdlight beam (e.g., another beam similar to beam 302) of the secondplurality of light beams (of the second scan) may have the firstposition in the particular spatial arrangement, and a fourth light beam(e.g., another beam similar to beam 306) of the second plurality oflight beams may have the second position in the particular spatialarrangement.

In these implementations, method 500 may optionally involve emitting(e.g., during the first scan) the first light beam prior to emitting thesecond light beam, and emitting (e.g., during the second scan) thefourth light beam prior to emitting the third light beam. For example,the order of emission of the light beams in the particular spatialarrangement during the first scan may be different from the order ofemission of the light beams in the particular spatial arrangement duringthe second scan.

In some examples, as noted above, a device of method 500 (e.g., device100, etc.) may include a transmitter that emits the first plurality oflight beams of the first scan in a particular spatial arrangement, andemits the second plurality of light beams of the second scan in the sameparticular spatial arrangement.

In some implementations, method 500 involves intercepting (e.g., byreceiver 114 of device 100, etc.) light from the FOV illuminated by thetransmitter. Referring back to FIG. 1 for example, a first detector ofdetectors 110 may be aligned with a first portion of the FOV illuminatedby a first beam of the plurality of beams described at block 502, asecond detector of detectors 110 may be aligned with a second portion ofthe FOV illuminated by a second beam of the plurality of beams, and soon.

IV. Example Timing Diagrams

FIG. 6A illustrates conceptual timing diagrams for a first scan 600 of aFOV, according to example embodiments. In particular, FIG. 6A showstiming diagrams for transmit/receive signals associated with multiplechannels (labeled as CH1, CH2, CH3, CH4) of an example device or systemherein (e.g., devices 100, 200, etc.). Each channel may be configured toscan a respective portion of a FOV. Referring back to FIG. 3 forexample, transmit signal 602 of CH1 may indicate emission of a pulse orbeam 302 at t=500 ns, transmit signal 604 of CH2 may indicate emissionof beam 304 at t=125 ns, transmit signal 606 of CH3 may indicateemission of beam 306 at t=375 ns, and transmit signal 608 of CH4 mayindicate emission of beam 308 at t=250 ns.

Thus, in line with the discussion above, an example system may scanrespective portions of a FOV using a spatial arrangement oftransmit/receive channels that emit signals at varying (e.g., dithered,etc.) times within an emission time period of first scan 600. Forinstance, in the scenario shown, the emission time period (500 ns) offirst scan 600 may have a start time of t=0 ns and an end time of t=500ns. Further, as shown, a detection time period (2000 ns) of first scan600 begins after the emission period lapses (at t=500 ns).

During the detection time period (e.g., from t=500 ns to t=2500 ns),each channel may listen for returning reflections of its respectivetransmitted signal. For instance, in the scenario shown, CH1 may detectreceive signal 622 at t=1500 ns. Thus, an example system or deviceherein may determine a distance “d” to an object that reflected aparticular receive signal detected by a particular channel as:

d=c*(channel_detection_time−channel_emission_time)/2;

where c is the speed of light (and/or other signal type of transmitsignal 602 such as sound, etc.). Thus, for CH1 in this scenario,d=c*(1500 ns−500 ns)/226 150 meters. In turn, an example system thatperforms the first scan 600 may determine that an object is present inthe portion of the FOV scanned by CH1 at a distance of 150 meters fromthe system. Similarly, the system can determine distances to objectspresent in respective portions of the FOV scanned by CH2, CH3, CH4 basedon the respective channel emission times (e.g., of signals 604, 606,608) and the respective channel detection times.

As noted above however, in some scenarios, a reflected portion of atransmit signal from a first channel may be spuriously detected by asecond channel. For instance, in a scenario where a retroreflector (orother strong reflector) is scanned by the first channel, portions of thereflected signal from the retroreflector may have sufficient energy tobe detected by the second channel as well.

For example, consider a scenario where transmit signal 602 is reflectedby a retroreflector and detected at CH1 as a (relatively strong) receivesignal 622. In this scenario, portions of the reflected signal from theretroreflector may also be detected spuriously at CH2 and CH3 as,respectively, (relatively weaker) receive signals 624 and 626. In someexamples, the (spurious) receive signals 624 and 626 may interfere with(and/or prevent) detection of non-spurious receive signals (not shown)that also arrive at t=1500 ns in CH2 and CH3.

However, in line with the discussion above, the effect of the spurioussignals on the quality of the scan can be mitigated by varying therespective channel emission times during the emission period. Forinstance, a system that computes distance to an object associated withspurious signal 624 may determine a distance of d=c*(1500 ns−125ns)/2≈206 meters in the portion of the FOV scanned by CH2. Similarly,the computing system may compute a distance of d=c*(1500 ns−375ns)/2≈169 meters for the spurious receive signal 626 in CH3. Thus, withthis arrangement, the errors associated with the spurious signaldetections 624 and 626 may be spread over a range of distances from thescanning device.

Whereas, in an alternative implementation, if transmit signals 604 (ofCH2) and 606 (of CH3) where instead transmitted at the same time (t=500ns) as the emission time of transmit signal 602 (of CH1), then all threechannels (CH1, CH2, CH3) would perceive presence of the retroreflectorat the same distance of d=150 meters in their respective portions of theFOV. As a result, in the alternative implementation, a relatively largerportion of the scanned FOV at d=150 meters would be affected by errorsassociated with the spurious signals, as compared to the implementationdescribed in FIG. 6A (where the respective channel emission times arevaried and/or dithered during the emission time period).

As noted above, some example methods herein involve obtaining a sequenceof scans of a FOV. For instance, an example system that performs thefirst scan 600 may then perform a second scan, which begins after thedetection period of the first scan lapses (i.e., at or after t=2500 ns),and so on. In some examples, the second scan may have a similar emissionperiod (500 ns), in which each of CH1, CH2, CH3, CH4 emits anotherrespective transmit signal (e.g., pulse, beam, etc.), followed by asimilar detection period (2000 ns). In one example, the system may beconfigured to obtain the sequence of scans periodically. For instance,each scan may be assigned a predetermined scanning period (e.g., 5microseconds, 10 microseconds, etc.). In some instances, each scanningperiod may be divided into a series of time windows (e.g.,initialization time period, background and/or noise detection timeperiod, signal emission time period, reflected signal detection timeperiod, data collection time period, etc.). However, for convenience indescription, FIG. 6A only shows the emission period and the detectionperiod of the first scan 600.

FIG. 6B illustrates conceptual timing diagrams for a second scan 650 ofthe FOV, according to example embodiments. For instance, second scan 650may be the second scan subsequent to first scan 600 in the sequence ofscans described above. To that end, transmit signals 652, 654, 656, 658and receive signals 672, 674, 676 may be similar, respectively, totransmit signals 602, 604, 606, 608 and receive signals 622, 624, 626 offirst scan 600.

Referring back to FIG. 3 for example, transmit signal 652 may indicateemission of another pulse or beam 302 at t=5000 ns, transmit signal 654of CH2 may indicate emission of another beam 304 at t=5500 ns, transmitsignal 656 of CH3 may indicate emission of another beam 306 at t=5125ns, and transmit signal 658 of CH4 may indicate emission of another beam308 at t=5375 ns.

As noted above, some example systems herein may obtain the sequence ofscans periodically or intermittently. For the sake of example, considera scenario where the illustrations of FIGS. 6A-6B involve an examplesystem configured to obtain the sequence of scans periodically (i.e.,one scan every 5 microseconds). In this scenario, similarly to firstscan 600, second scan 650 is shown to have a similar emission period(500 ns) from t=5000 ns to t=5500 ns, followed by a similar detectionperiod (2000 ns) from t=5500 ns to t=7500 ns.

However, as shown, the transmit signals of CH1, CH2, CH3, CH4 areassigned different time offsets within the emission period of secondscan 650 as compared to the time offsets assigned to the correspondingtransmit signals of first scan 600.

Referring back to FIG. 6A for example, transmit signal 602 (of CH1) isassigned a time offset of 500 ns−0 ns=500 ns from the start time (t=0ns) of the emission period of first scan 600, transmit signal 604 (ofCH2) is assigned a time offset of 125 ns−0 ns =125 ns, transmit signal606 (of CH3) is assigned a time offset of 375 ns−0 ns=375 ns, andtransmit signal 608 (of CH4) is assigned a time offset of 250 ns−0ns=250 ns.

In contrast, returning now to FIG. 6B, transmit signal 652 (of CH1) isassigned a time offset of 5000 ns−5000 ns=0 ns from the start time(t=5000 ns) of the emission period of second scan 650, transmit signal654 (of CH2) is assigned a time offset of 5500 ns−5000 ns=500 ns,transmit signal 656 (of CH3) is assigned a time offset of 5125 ns−5000ns=125 ns, and transmit signal 658 (of CH4) is assigned a time offset of5375 ns−5000 ns=375 ns.

In some examples, in accordance with the present disclosure, suchvarying (e.g., dithering) of relative channel emission times withinrespective emission periods of a sequence of scans may facilitateidentification and/or mitigation of errors associated with spurioussignal detection. For example, consider the scenario described above forFIG. 6A, where a retroreflector in the portion of the FOV scanned by CH1causes the detection of non-spurious receive signal 622 in CH1 as wellas spurious receive signals 624 (in CH2) and 626 (in CH3) during thefirst scan 600. Continuing with this scenario, returning now to FIG. 6B,the retroreflector may similarly result in the detection (at t=6000 ns)of non-spurious receive signal 672 (in CH1) and spurious receive signals674 (in CH2) and 676 (in CH3).

In this scenario, the distance to the retroreflector perceived by CH1during the second scan 650 may be d=c*(6000−5000)/2≈150 meters, which isthe same as the distance computed for CH1 during the first scan 600.However, due to the change in the emission time offsets associated withtransmit signals 652, 654, 656, the distances to the retroreflectorcomputed for CH2 and CH3 in the second scan 650 may be different thanthe corresponding distances computed in the first scan 600. Forinstance, the distance computed for CH2 in the second scan 650 may bed=c*(6000−5500)/2≈75 meters (compared to 206 meters in the first scan600); and the distance computed for CH3 in the second scan 650 may bed=c*(6000−5125)/2≈131 meters (compared to 169 meters in the first scan600).

Thus, with this arrangement for example, consecutive detections of anobject that is actually present in a portion of the FOV scanned by aparticular channel may remain “coherent” (e.g., the perceived distanceto the object may remain substantially the same in consecutive scans bythe particular channel). On the other hand, consecutive detections of anobject that is not actually present in the portion of the FOV scanned bythe particular channel may be “incoherent” (e.g., the perceived distanceto the object may change in consecutive scans by the particularchannel). In various examples, a system herein can improve the qualityof LIDAR sensor data based on the incoherent nature of the spurioussignals.

In one example, a device herein may determine that a received signal ata first channel has signal characteristics associated with presence of aretroreflector. For instance, as shown in FIG. 6B, the device may detectthat receive signal 672 in CH1 has a signal intensity greater than athreshold (e.g., a sufficiently high intensity expected when aretroreflector is present in the portion of the FOV scanned by the firstchannel). In response to such determination, the device may identifyother signals that were received at other channels (e.g., signals 674and 676) at a same time (t=6000 ns) when signal 672 was received at thefirst channel. The device may then store an indication of the identifiedother signals as potential spurious signal detections by the otherchannels (CH2 and CH3). Upon further processing of the sensor data fromthe LIDAR (e.g., by a computing device, etc.) for instance, thepotential spurious signal detections can be removed from the sensor data(or otherwise modified) if the received signal at the first channel isdetermined to be a reflection from a retroreflector.

Additionally, due to the incoherent nature of the potential spurioussignals, the effect of removing the spurious signals on the quality ofsensor data from a particular channel can be mitigated. Referring backto FIG. 6A for example, removal of data associated with spurious signal624 may result in a missing measurement from CH2 at the distance of 206meters in the first scan 600. However, during the second scan 650, CH2can scan for objects at the distance of 206 meters even if spurioussignal 674 is also removed because spurious signal 674 corresponds to adistance of 75 meters in the second scan 650 (instead of a distance of206 meters). On the other hand, if spurious signals 624 and 674 wereinstead coherent, then CH2 would be blinded from detecting true objectsat a particular distance (e.g., 75 meters) during several consecutivescans by CH2.

Accordingly, some example methods herein (e.g., methods 400, 500) mayinvolve determining that a first signal received by a first detector hasan intensity greater than a threshold, identifying one or moreadditional signals received by one or more other detectors at a sametime as a time of receipt of the first signal, and storing an indicationof the one or more additional signals.

Alternatively or additionally, some example methods herein (e.g.,methods 400, 500) may involve identifying an error detection based on acomparison of sensor data collected during a sequence of scans of a FOV.Referring back to FIG. 1 for example, a computing device (e.g.,controller 104) may compare distance measurements obtained using a firstdetector of detectors 110 in a plurality of successive scans of thesequence of scans. If the distance measurements indicated by the firstdetector are coherent (e.g., within a threshold tolerance range), thenthe computing device may determine that the measurements associated withthe plurality of scans indicate presence of an actual object in theportion of the FOV scanned by the first detector. Whereas, if thedistance measurements are incoherent (e.g., outside the thresholdtolerance range), then the computing device may determine that themeasurements may be associated with channel cross-talk or other sourceof noise.

To that end, in some examples, a method herein (e.g., methods 400, 500)may also involve filtering sensor data obtained from a receiver (e.g.,receiver 114) based on a comparison of distance measurements associatedwith the sequence of scans. For example, the sensor data can be prunedto remove given data associated with spurious signals (associated withincoherent distance measurements in successive scans of the sequence ofscans). For instance, referring back to FIG. 1, device 100 may analyzethe sensor data to remove data points (e.g., signal detections, etc.)that are inconsistent over a given number (e.g., two, three, etc.) ofsuccessive scans by a same detector of detectors 110.

In accordance with the present disclosure, the various devices, systems,and methods described herein can be implemented in a variety ofdifferent ways.

In one particular implementation, a device herein (e.g., device 100) mayinclude a controller (e.g., controller 104) configured to obtain asequence of scans (e.g., scans 600, 650, etc.) of a FOV (e.g., FOV 300)of the device. The device may also include a transmitter (e.g.,transmitter 106) configured to emit, for a first scan (e.g., scan 600)of the sequence of scans, a first plurality of light pulses (e.g.,pulses 602, 604, 606, 608, etc.) in a particular spatial arrangement(e.g., arrangement of beams 302, 304, 306, 308, 312, 318, etc., shown inFIG. 3, or any other arrangement), and according to a first plurality oftime offsets between emission times of the plurality of light pulses.

Thus, although some examples herein describe the time offsets as beingcomputed relative to a start time (or end time) of an emission timeperiod, other examples may involve computing the time offsets betweenthe emission times of the emitted pulses/beams, among otherpossibilities. Referring back to FIG. 6A for example, a first timeoffset of the plurality may be between pulse 602 and pulse 604 (e.g.,500−125=375 ns), a second time offset may be between pulse 602 and 606(e.g., 500−375=125 ns), and so on.

Continuing with this implementation, the device may also include areceiver (e.g., receiver 114) that includes a plurality of detectors(e.g., detectors 110). Each detector of the plurality of detectors maybe aligned with a respective portion of the FOV illuminated by arespective light pulse of the plurality of light pulses. Referring backto FIG. 3 for example, a first detector of the plurality may be alignedwith a first portion of FOV 300 that is illuminated by pulse 302, asecond detector may be aligned with a second portion of FOV 300 that isilluminated by pulse 304, and so on. For instance, light from FOV 300can be focused by one or more optical elements (e.g., optical elements106), such as lenses and the like, onto an image plane where theplurality of detectors are located. In this instance, the first detectorcan be located at a region of the image plane where light from the firstportion of FOV 300 (illuminated by pulse 302) is focused, and so on.

In some examples, the sequence of scans may include at least the firstscan (e.g., scan 600) and a second scan (e.g., scan 650). In theseexamples, the transmitter may also be configured to emit (for the secondscan) a second plurality of light pulses in the same particular spatialarrangement as the first plurality of light pulses (e.g., arrangementshown in FIG. 3, or any other arrangement), and according to a secondplurality of time offsets (e.g., different than the first plurality oftime offsets used in the first scan). As shown in FIG. 6B for example, athird time offset (of the second plurality of time offsets) may bebetween light pulses 652 and 654 (e.g., 5000−5500=−500 ns), and so on.Thus, in this example, the time offsets between emission times of thelight pulses emitted in CH1 and CH2 may be varied between differentscans (e.g., 375 ns in the first scan, −500 ns in the second scan, etc.)in the sequence of scans. Similarly, in some examples, the time offsetsbetween emission times used for light pulses between one or more otherpairs of channels (e.g., CH1/CH3, CH1/CH4, CH2/CH3, etc.) can also bevaried between scans, in line with the discussion above.

V. Conclusion

The particular arrangements shown in the Figures should not be viewed aslimiting. It should be understood that other implementations may includemore or less of each element shown in a given Figure. Further, some ofthe illustrated elements may be combined or omitted. Yet further, anexemplary implementation may include elements that are not illustratedin the Figures. Additionally, while various aspects and implementationshave been disclosed herein, other aspects and implementations will beapparent to those skilled in the art. The various aspects andimplementations disclosed herein are for purposes of illustration andare not intended to be limiting, with the true scope and spirit beingindicated by the following claims. Other implementations may beutilized, and other changes may be made, without departing from thespirit or scope of the subject matter presented herein. It will bereadily understood that the aspects of the present disclosure, asgenerally described herein, and illustrated in the figures, can bearranged, substituted, combined, separated, and designed in a widevariety of different configurations.

1. A device comprising: a plurality of emitters including at least afirst emitter and a second emitter, wherein the first emitter emitslight that illuminates a first portion of a field-of-view (FOV) of thedevice, and wherein the second emitter emits light that illuminates asecond portion of the FOV; and a controller that obtains a scan of theFOV, wherein the controller obtaining the scan of the FOV comprises thecontroller causing each emitter of the plurality of emitters to emit arespective light pulse during an emission time period associated withthe scan, wherein the emission time period has a start time and an endtime, and wherein the controller causing each emitter to emit therespective light pulse comprises the controller: causing the firstemitter to emit a first-emitter light pulse at a first-emitter timeoffset from the start time of the emission time period, and causing thesecond emitter to emit a second-emitter light pulse at a second-emittertime offset from the start time of the emission time period; and aplurality of detectors, wherein the controller obtaining the scan of theFOV comprises the controller operating the plurality of detectors tomeasure light from the FOV incident on the plurality of detectors duringa detection time period that begins after the end time of the emissiontime period.
 2. (canceled)
 3. The device of claim 1, further comprising:a lens that focuses the light from the FOV for receipt by the pluralityof detectors, wherein a first detector of the plurality of detectors isarranged to intercept a first portion of the focused light that includesa reflection of the light emitted by the first emitter, and wherein asecond detector of the plurality of detectors is arranged to intercept asecond portion of the focused light that includes a reflection of thelight emitted by the second emitter.
 4. The device of claim 1, wherein adifference between the first-emitter time offset and the second-emittertime offset is at least 2.5 nanoseconds.
 5. The device of claim 1,wherein the scan obtained by the controller is a first scan, wherein thecontroller obtains a sequence of scans of the FOV including at least thefirst scan and a second scan subsequent to the first scan.
 6. The deviceof claim 5, wherein the controller obtaining the second scan comprisesthe controller modifying the first-emitter time offset.
 7. The device ofclaim 6, wherein the controller obtaining the second scan furthercomprises the controller modifying the second-emitter time offset. 8.The device of claim 7, wherein the emission time period of the firstscan is a first emission time period, and wherein the controllerobtaining the second scan comprises the controller: causing the firstemitter to emit another first-emitter light pulse at the modifiedfirst-emitter time offset from a start time of a second emission timeperiod associated with the second scan; and causing the second emitterto emit another second-emitter light pulse at the modifiedsecond-emitter time offset from the start time of the second emissiontime period.
 9. The device of claim 5, wherein the controller determinesa pseudo-random time offset sequence, and wherein the controller adjuststhe first-emitter time offset for one or more scans of the sequence ofscans according to the determined pseudo-random time offset sequence.10. The device of claim 9, wherein the sequence of scans is a firstsequence of scans, wherein the controller obtains a second sequence ofscans of the FOV after the first sequence of scans, and wherein thecontroller adjusts the second-emitter time offset for one or more scansof the second sequence of scans according to the determinedpseudo-random time offset sequence.
 11. The device of claim 1, furthercomprising: a transmitter that includes the plurality of emitters,wherein the transmitter transmits, during the emission time period ofthe scan, a plurality of light beams in a spatial arrangement thatdefines the FOV of the device, wherein the light emitted by the firstemitter includes at least a first light beam of the plurality of lightbeams, and wherein the light emitted by the second emitter includes atleast a second light beam of the plurality of light beams.
 12. Thedevice of claim 11, wherein the light emitted by the first emitter alsoincludes a third light beam of the plurality of light beams.
 13. Thedevice of claim 12, further comprising one or more optical elements thatdirect: a first portion of the light emitted by the first emitter towarda first position of the first light beam in the spatial arrangement, anda second portion of the light emitted by the first emitter toward asecond position of the third light beam in the spatial arrangement. 14.A method comprising: causing a plurality of emitters to emit a pluralityof light pulses during a first emission time period associated with afirst scan of a field-of-view (FOV), wherein a first emitter of theplurality of emitters is configured to illuminate a first portion of theFOV, wherein a second emitter of the plurality of emitters is configuredto illuminate a second portion of the FOV, and wherein causing theplurality of emitters to emit the plurality of light pulses comprises:causing the first emitter to emit a first-emitter light pulse at afirst-emitter time offset from an end time of the first emission timeperiod, and causing the second emitter to emit a second-emitter lightpulse at a second-emitter time offset from the end time of the firstemission time period; and obtaining the first scan based on measurementsof light from the FOV received by a plurality of detectors during afirst detection time period that begins after the end time of the firstemission time period.
 15. The method of claim 14, further comprising:obtaining a sequence of scans of the FOV including at least the firstscan and a second scan subsequent to the first scan; and modifying thefirst-emitter time offset for the second scan, wherein obtaining thesecond scan comprises causing the first emitter to emit anotherfirst-emitter light pulse at the modified first-emitter time offset froman end time of a second emission time period associated with the secondscan, and wherein obtaining the second scan is based on measurements oflight from the FOV received by the plurality of detectors during asecond detection time period that begins after the end time of thesecond emission time period.
 16. The method of claim 15, furthercomprising: modifying, for the second scan, the second-emitter timeoffset, wherein obtaining the second scan comprises causing the secondemitter to emit another second-emitter light pulse at the modifiedsecond-emitter time offset from the end time of the second emission timeperiod.
 17. The method of claim 14, further comprising: determining apseudo-random time offset sequence; obtaining a sequence of scans of theFOV including the first scan; and selecting, for each scan of thesequence of scans, the first-emitter time offset from the pseudo-randomtime offset sequence based on an order of the scan in the sequence ofscans.
 18. The method of claim 14, wherein a first detector of theplurality of detectors is arranged to receive light from the firstportion of the FOV illuminated by the first emitter, the method furthercomprising: detecting, via the first detector, a first-detector lightpulse at a first detection time during the first detection time period;and associating the first-detector light pulse with presence of aretroreflector in the first portion of the FOV illuminated by the firstemitter.
 19. The method of claim 18, wherein associating thefirst-detector light pulse with presence of the retroreflector is basedon at least an intensity of the first-detector light pulse being greaterthan a threshold intensity.
 20. The method of claim 19, furthercomprising: determining the threshold intensity based on thefirst-emitter time offset and the first detection time.
 21. The methodof claim 18, wherein a second detector of the plurality of detectors isarranged to measure light from the second portion of the FOV illuminatedby the second emitter, the method further comprising: detecting, via thesecond detector, a second-detector light pulse at a second detectiontime during the first detection time period.
 22. The method of claim 21,further comprising: based on the first detection time being within apredetermined threshold to the second detection time, associating thesecond-detector light pulse with the presence of the retroreflector inthe first portion of the FOV.
 23. The method of claim 21, furthercomprising: based on a difference between the first detection time thesecond detection time being greater than a predetermined threshold,associating the second-detector light pulse with presence of an objectin the second portion of the FOV.
 24. A device comprising: a transmitterthat emits, during a first emission time period associated with a firstscan of a field-of-view (FOV) of the device, a first plurality of lightbeams spatially arranged to illuminate respective portions of the FOV,wherein the first emission time period has a start time and an end time,wherein the transmitter emits a first light beam of the first pluralityof light beams toward a first portion of the FOV at a first-portion timeoffset from the start time of the first emission time period, andwherein the transmitter emits a second light beam of the first pluralityof light beams toward a second portion of the FOV at a second-portiontime offset from the start time of the first emission time period; areceiver that intercepts light from the FOV illuminated by thetransmitter; and a controller that operates the transmitter and thereceiver to obtain the first scan, wherein the controller operating thereceiver comprises the controller obtaining, from the receiver,measurements of the light from the FOV intercepted by the receiverduring a detection time period that begins after the end time of thefirst emission time period.
 25. (canceled)
 26. The device of claim 24,wherein the transmitter emits, during a second emission time periodassociated with a second scan of the FOV, a second plurality of lightbeams.
 27. The device of claim 26, wherein the transmitter emits a thirdlight beam of the second plurality of light beams toward the firstportion of the FOV at a modified first-portion time offset from a starttime of the second emission time period that is different than thefirst-portion time offset associated with the first scan.
 28. The deviceof claim 26, wherein the transmitter emits the first plurality of lightbeams in a particular spatial arrangement, and emits the secondplurality of light beams in the particular spatial arrangement, whereinthe first light beam of the first plurality of light beams has a firstposition in the particular spatial arrangement, wherein the second lightbeam of the first plurality of light beams has a second position in theparticular spatial arrangement, wherein a third light beam of the secondplurality of light beams has the first position in the particularspatial arrangement, wherein a fourth light beam of the second pluralityof light beams has the second position in the particular spatialarrangement, wherein the transmitter, during the first scan, emits thefirst light beam prior to emitting the second light beam, and whereinthe transmitter, during the second scan, emits the fourth light beamprior to emitting the third light beam.
 29. The device of claim 24,further comprising a controller that obtains a sequence of scans of theFOV including the first scan, wherein the controller determines apseudo-random time offset sequence, and wherein the controller obtainingthe sequence of scans comprises the controller adjusting thefirst-portion time offset for each scan of the sequence of scansaccording to the determined pseudo-random time offset sequence.
 30. Adevice comprising: a controller that obtains a sequence of scans of afield-of-view (FOV) of the device; a transmitter that emits, for a firstscan of the sequence of scans, a first plurality of light pulses in aparticular spatial arrangement and according to a first plurality oftime offsets between emission times of the first plurality of lightpulses during a first emission time period, wherein the first emissiontime period has a start time and an end time; and a receiver thatincludes a plurality of detectors, wherein each detector of theplurality of detectors is aligned with a respective portion of the FOVilluminated by a respective light pulse of the first plurality of lightpulses, and wherein the receiver measures light from the FOV incident onthe plurality of detectors during a first detection time period thatbegins after the end time of the first emission time period.
 31. Thedevice of claim 30, wherein the sequence of scans includes at least thefirst scan and a second scan subsequent to the first scan, and whereinthe transmitter emits, for the second scan, a second plurality of lightpulses in the particular spatial arrangement and according to a secondplurality of time offsets between emission times of the second pluralityof light pulses during a second emission time period.